 Once the malaria parasite enters the erythrocytic stage, it can adversely affect blood cells, making it possible to contract the parasite through infected blood.Chloroquine may be used where the parasite is still sensitive, however many malaria parasite strains are now resistant.Mefloquine ("Lariam"), or doxycycline (available generically), or the combination of atovaquone and proguanil hydrochloride ("Malarone") are frequently recommended.In choosing the agent, it is important to weigh the risk of infection against the risks and side effects associated with the medications.